Related Party Transactions - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Related Party Transaction [Line Items]
Expense incurred as result of multiple service agreements	$ 2,763	$ 2,707
Period of bear interest at commercial paper rate	30 days
Due to affiliates	$ 8,514	6,148	$ 6,148
Interest expense accrued and/or paid due to intercompany arrangements	1	0
Interest income accrued and/or received due to intercompany arrangements	54	7
AEGON USA Realty Advisors, LLC
Related Party Transaction [Line Items]
Expense incurred as result of multiple service agreements	11	51
AEGON USA Investment Management LLC
Related Party Transaction [Line Items]
Expense incurred as result of multiple service agreements	617	491
Transamerica Capital, Inc.
Related Party Transaction [Line Items]
Expense incurred as result of multiple service agreements	6,110	5,558
Transamerica Asset Management, Inc.
Related Party Transaction [Line Items]
Expense incurred as result of multiple service agreements	0	79
Distribution and shareholder services agreement
Related Party Transaction [Line Items]
Revenue from participation agreement	811	$ 600
Transamerica Life Insurance Company
Related Party Transaction [Line Items]
Expense incurred as result of multiple service agreements	118
1.10 % Note Payable
Related Party Transaction [Line Items]
Intercompany short-term note payable or receivable	$ 10,000
Interest on intercompany note payable/receivable	1.10%
Intercompany short-term note receivable, date	Oct. 20, 2017